1. Field of the Invention
The present invention relates generally to a cathode ray tube, and is directed more particularly to a flat panel type cathode ray tube.
2. Description of the Prior Art
In the art, a flat panel type cathode ray tube is constructed as shown in FIG. 1. That is, a panel 2, which has a phosphor layer (not shown) coated on its inner surface and is contacted with and sealed to the front end edge of a funnel portion 1 to which is a neck 3 having an electron gun (not shown) therein is coupled, is made flat of, for example, a glass plate, so that the mechanical accuracy thereof is high. Further, a phosphor screen, for example, color phosphor screen can be formed on the inner surface of the flat panel 2 by the printing technique so that the cathode ray tube can be mass-produced and hence made inexpensive. However, the application of a high voltage to the inner surface of the panel 2 of such a flat panel type cathode ray tube proposes a problem. Especially, in the case of a high brightness cathode ray tube used as a color projector or the like, high voltage and large current are used therein so that the application of high voltage to the inner surface of the flat panel becomes a problem.
That is, in the case of a cathode ray tube in which a panel 12 having along its peripheral edge a so-called skirt portion 12a curved towards a funnel 11 is sealed to the front open end of the funnel 11, a conductive layer 13 which is formed on the inner surface of the panel 12 and supplied with a high voltage is generally formed to also cover the inner surface of the skirt portion 12a of the panel 12. While, the inner end of an anode button 14 provided through the funnel portion 11 is engaged with an anode contactor 15 made of a resilient metal plate. This anode contactor 15 is extended along the inner surface of the funnel portion 11 to the panel 12 in such a manner that the plate surface of the anode contactor 15 is substantially along the conductive layer 13 coated on the inner surface of the skirt portion 12a and a contactor 15a formed at the free end of the anode contactor 15 resiliently contacts the conductive layer 13. Thus, the high voltage applied to the anode button 14 is applied through the anode contactor 15 to the conductive layer 13 coated on the inner surface of the panel 12.
With the cathode ray tube in which the panel 12 has the skirt portion 12a and the conductive layer 13 is extended to the inner surface of the skirt portion 12a as described above, since the plate surface of the contactor 15 made of the resilient metal leaf extends along the conductive layer 13 on the inner surface of the skirt portion 12a and the contactor 15a thereof contacts the conductive layer 13, the resiliency of the anode contactor 15 effectively contributes to the resilient contact between the anode contactor 15 and the conductive layer 13 to maintain good contact.
In the case of the flat panel type cathode ray tube described in connection with FIG. 1, since the panel 2 has no skirt portion along its peripheral portion, the contact between the anode contactor made of a resilient leaf and the conductive layer formed on the inner surface of the panel, which are described in connection with FIG. 2, is not in contact along the surface direction of the resilient leaf and hence it becomes difficult to make good resilient contact, which becomes a problem especially when it is applied to a high voltage and large current cathode ray tube.
In order to make good contact in the flat panel type cathode ray tube, if the contactor 15a provided at the free end of the anode contactor 15 made of the resilient leaf is bent inwards to be L-shaped and the bent end of the contactor 15 contacts the conductive layer on the inner surface of the flat panel, it is necessary that the length of the bent portion of the contactor be selected sufficiently long so as to obtain a sufficient resiliency which will contribute to the contact thereof with the conductive layer on the inner surface of the flat panel. This results in that the area of the panel on which the image of the contactor is projected increases and hence the ineffective area of the picture screen also increases.